1. Field of the Invention
The present invention relates generally to reversible radio architecture, and more particularly, to a reversible Time Division Duplex (TDD) and/or Time Division Multiple Access (TDMA) radio architecture between Transmission (Tx) and Reception (Rx) functions in a mobile communication system.
2. Description of the Related Art
The Long Term Evolution (LTE) and LTE-Advanced (LTE-A) mobile communication systems, developed by the 3rd Generation Partnership Project (3GPP) standardization organization, adopt Orthogonal Frequency Division Multiplexing (OFDM) technology instead of the conventional Code Division Multiple Access (CDMA) technology. OFDM is a multi-carrier transmission scheme using multiple carriers for data transmission.
The LTE and LTE-A standard techniques are divided into TDD and Frequency Division Duplex (FDD) air-interface systems. In the FDD system, two different frequencies are used for uplink and downlink transmission, and the Base Station (BS) and User Equipment (UE) may send and receive data simultaneously. In the TDD system, the same frequency is used for uplink and downlink transmission, and the BS and UE cannot send and receive data simultaneously.
FIG. 1 illustrates architecture for a TDD/TDMA RF unit 100 according to the prior art.
In FIG. 1, a signal transmitted or received by a Tx/Rx antenna 105 is sent to a Tx/Rx switch 110, which controls the TDD/TDMA RF unit 100 to switch between uplink and downlink operations. When the TDD/TDMA RF unit 100 is applied to a UE, the Tx/Rx switch 110 performs switching between downlink Rx and uplink Tx, whereas when the TDD/TDMA RF unit 100 is applied to a BS, the Tx/Rx switch 110 performs switching between downlink Tx and uplink Rx.
The Tx/Rx switch 110 includes a filter and a Power Amplifier (PA). The filter serves two functions in a TDD or TDMA transceiver: (1) Rejection of undesired signals at frequencies different from the desired signals during the Rx period. This rejection reduces the effect which the undesired receive signals have on the performance of the desired receive signals. (2) Reduction of transmit frequency sidebands which can cause interference to other transceivers during the Tx period. Meanwhile, the PA strengthens the transmit (outgoing) signal. The PA is only turned on during the Tx period; otherwise, it is turned off so as to not interfere with the receive function.
On the Rx side, the Tx/Rx Switch 110 sends the signal to a Low-Noise Amplifier 115, where the signal is processed and sent to a Down-Converter 120 (i.e. Mixer) where the signal is down-converted. The resultant signal is sent to an Rx Filter 125, such as a Wi-Fi or Bluetooth® (BT) Receiver, which filters and sends the signal to an Analog-to-Digital Converter (ADC) 130 where it is converted to digital and then output. A Local Oscillator 150 may also provide a signal to the Down-Converter 120. On the Tx side, a Digital-to-Analog Converter (DAC) 135 converts a digital signal to analog and sends the resultant signal to a Tx Filter 140, such as a Wi-Fi or BT Transmitter, for filtering. The filtered signal is sent to an Up-Converter 145 (i.e. Mixer), where the signal is up-converted and sent to a Driver 155, which amplifies the signal and sends the amplified signal to the Tx/Rx Switch 110 for transmission. The Local Oscillator 150 may also provide a signal to the Up-Converter 145.
The conventional TDD/TDMA RF unit, as applied to a BS for example, can perform either downlink Tx or uplink Rx of data using physically separate circuit blocks alternately in time, but is not adapted to perform both Tx and Rx of data re-using the same circuits for both functions. As such, there is a need in the art for RF architecture that enables both Tx and Rx functions using the same components, in a mobile communication system.